One type of pouring spout commonly found on industrial size pails and cans consists of a collapsible plastic spout having a flexible wall portion which allows the spout to be raised from a compact stored or nested condition to a fully extended pouring position. The spout neck is exteriorly threaded to receive a screw cap for reclosing. To assure against leakage and pilfering under shipping or storage conditions, the spout neck is initially closed off with an integrally formed sealing diaphragm. In the interest of convenience and sanitary opening, these diaphragms are commonly not cut out with a knife but instead are provided with a peripheral tearing zone or score line and a pull member for removal.
A close structure balance must be maintained in determining the proper thickness of remaining plastic material at the peripheral score line. If this thickness is too great, tearing becomes difficult and erratic. If too thin, accidental rupturing will occur. This structure balance has now become even more critical with the more recent need to meet UN (IMCO) packaging requirements calling for a six foot drop test. Dropping a fluid filled five gallon pail equipped with the closure from a height of six feet creates a substantial rupturing force by the fluid acting on the diaphragm and transmitted to that thin tearing zone of plastic surrounding the sealing diaphragm. At the moment of impact, this force causes a severe deflection or bulging of the disc like sealing diaphragm such that rupture at the intentionally weakened tearing zone will frequently occur. Avoidance of tearing zone rupture is the principal concern of this invention.